Anal incontinence is a common problem that occurs in both men and women, though is certainly more prevalent in women after vaginal childbirth, presumably the result of trauma to pelvic floor muscles, supporting fascia and nerves. Fecal incontinence affects an estimated 7.6 percent of women between the ages of 30-90. The prevalence increases with age, affecting 3.6 percent of women between 30-39 and 15.2 percent of women between 80-90. Several factors contribute to anal continence, including the resting tone of the external and internal anal sphincters, as well as the position of the levator ani muscles, especially the puborectalis muscle, which forms a sling around the rectum and is responsible for the so-called “ano-rectal angle,” which keeps stool in the rectum until voluntary defecation relaxes the puborectalis muscle and straightens the angle, allowing stool to move towards the anus.
Defecation is often aided by expulsive abdominal forces. Anal incontinence may occur as the result of several mechanisms, including direct damage to the internal or external anal sphincters (from iatrogenic episiotomy or spontaneous lacerations during vaginal delivery), or to the levator ani muscles. It may also result from indirect injury of these muscles through denervation of the nerves that supply these muscles. Treatment of this problem has centered on pelvic floor rehabilitation, dietary changes, or surgical correction. Surgery has been used to treat specific defects in the anal sphincters, such as external anal sphincteroplasty. Success rates of only 50% or less are generally reported for these procedures on long-term follow-up.
More recently, an artificial anal sphincter has been used to bypass these muscles, though this surgery involves fairly extensive dissection and requires the patient to depress a subcutaneous valve which temporarily deflates the sphincter cuff and allows voluntary defecation. This procedure is performed in very few centers in the U.S., and even in experienced hands, complications occur frequently. Dynamic graciloplasty, which involves mobilization and wrapping of the gracilis muscle around the anorectum is now another accepted procedure although is remains complex and requires extensive experience to obtain good results. More recently, sacral nerve stimulation has been used with some success to treat fecal incontinence, though the mechanism of success in these patients remains unclear, and may not be appropriate in women with obvious anatomic abnormalities, such as anal sphincter or levator muscle disruptions.
In addition, many women report other symptoms of bowel dysfunction, such as constipation and incomplete bowel emptying. For some women, these symptoms are due to either an anterior rectocele (a hernia of the rectum into the vaginal canal), or due to a defect in the levator ani muscles, which results in descent of the levator plate and/or perineum with abdominal straining. In addition, patients may be noted to have a defect in the posterior aspect of the rectum, or a posterior rectocele. There are very few treatment options for this condition, though retrorectal levatorplasty has been used in the past. In this procedure, an incision is made between the anus and the coccyx and the levator muscles are exposed bilaterally. Sutures are then placed in the levator muscles to plicate them together in the midline.
Pelvic organ prolapse is a condition where organs, such as the uterus, the rectum, or the bladder, fall down or slip out of place within a person's body. It is commonly used in reference to organs protruding through a woman's vagina, but prolapse may occur within men as well. In general, the levator ani muscles provide the main support for pelvic organs including, for example, the rectum, the vagina, and the urethra. In a person with a normal pelvis, the levator ani muscles keep the pelvic floor closed, thereby allowing the pelvic and abdominal organs to rest on the levator ani muscles. This also significantly reduces the tension that would otherwise be placed on the fascia and ligaments that support the pelvic organs. The posterior portion of the levator ani muscles arise from the area of the tendinous arch. The anterior portion of the levator ani muscles arise from the superior pubic rami and from the anterior end of the obturator internus muscles. This portion forms the pubococcygeus muscle and the puborectalis muscle. The pubococcygeus muscle is a generally thick, U-shaped muscle through which the urethra, vagina, and rectum transverse. The pubococcygeus muscle supports these structures at rest, and helps to augment the endopelvic fascia during coughing or straining. The puborectalis muscle is structured to act as a sling support for the rectum, and includes two ends that attach to the anterior side of the symphysis pubis. The levator ani muscle group includes an opening through which the vagina and urethra pass, which is referred to as the urogenital hiatus. Similarly, the levator ani muscle group includes an opening through which the rectum passes, which is referred to as the rectal hiatus.
In a normal woman, the pelvic floor muscles support most of the weight of the pelvic organs, such as the vagina, uterus, bladder, and rectum. Additionally, the various pelvic fascia and ligaments stabilize these structures in position. When the normal anatomic relationships in the pelvis are disrupted, or if injuries occur, dysfunctions such as urinary incontinence, fecal incontinence, or prolapse of the pelvic organs, may occur. For example, if one of the levator ani muscles is damaged, the muscle may be unable to adequately support the weight of the pelvic organs. This will result in a disproportionate amount of the pelvic organ weight being placed onto the pelvic ligaments, which are significantly weaker than the fibrous tissue of the ligaments that connect bones. In particular, the pelvic ligaments are more accurately described as thickening of the endopelvic fascia tissue, which is composed of collagen, smooth muscle, elastin, and fibrovascular bundles. These ligaments are not designed to carry the increased load resulting from problems in the pelvic floor. As a result, these ligaments may eventually fail. The failure or damage to the pelvic floor ligaments may cause, for example, the bladder, rectum, or uterus to prolapse through the vagina. Similarly, expansion of or damage to the levator or rectal hiatus may result in the bladder, vagina, or rectum prolapsing through the hiatus.
As stated previously, pelvic prolapse conditions result from the weakness or damage to the normal pelvic-support systems. In general, the main categories of pelvic prolapse include cystocele, rectocele, enterocele, uterine prolapse, and vaginal vault prolapse. The most common causes of these pelvic floor disorders in a female patient include child birth and removal of the uterus (hysterectomy). However, other contributing factors may include connective tissue defects, prolonged heavy physical labor, postmenopausal atrophy, neurogenic weakness of muscles, muscle weakness due to aging, and obesity.
A cystocele occurs when damage to the pubocervical fascia in the central or lateral areas (or both) allows the bladder to protrude into the vagina. Simply defined, a cystocele is a protrusion of the bladder into the vagina due to defects in pelvic support.
A rectocele is a bulge into the vagina caused by the rectum prolapsing through an attenuated rectovaginal septum. A rectocele is commonly a result of childbirth or chronic constipation. During childbirth, the rectovaginal septum and surrounding vaginal tissues are stretched and disrupted, which may cause weakness and stretching in these tissues. A rectocele typically forms a pocket just above the anal sphincter where stool may become trapped.
An enterocele is essentially a herniation of the small bowel into the vagina. Specifically, the peritoneal sac containing a portion of the small bowel extends into the rectovaginal space between the posterior surface of the vagina and the anterior surface of the rectum.
A uterine prolapse is the distention of the uterus and cervix outside the vagina. It is often associated with a rectocele, cystocele, or entrocele.
Finally, a vaginal vault prolapse is the distention of the vaginal apex after hysterectomy outside the vagina. It is also often associated with a rectocele, cystocele, or entrocele.